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Cyclic Dimethylsiloxanes as Pseudo Crown Ethers Syntheses and Characterization of Li(Me2SiO)5[Al{OC(CF3)3}4] Li(Me2SiO)6[Al{OC(CF3)3}4] and Li(Me2SiO)6[Al{OC(CF3)2Ph}4].

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[KD7]+ ions were unexpectedly isolated from reactions in
the presence of silicone grease,[13] although the mechanisms of
the reactions are unclear. In a reaction designed to give
Se6Ph2ACHTUNGRE[AlF]2 ([AlF] = Al{OCACHTUNGRE(CF3)3}4) from Se4ACHTUNGRE(AsF6)2, 2 LiACHTUNGRE[AlF], and Se2Ph2 in the presence of silicone grease, we
unexpectedly obtained crystals of LiD6ACHTUNGRE[AlF]. Subsequently,
we prepared LiD5ACHTUNGRE[AlF], LiD6ACHTUNGRE[AlF], and LiD6ACHTUNGRE[AlPhF] ([AlPhF] =
Al{OCACHTUNGRE(CF3)2Ph}4) in high yield by the reaction of LiACHTUNGRE[AlF] or
LiACHTUNGRE[AlPhF] with D5 or D6 in CH2Cl2 solution [Eq. (1)].
Host?Guest Complexes
DOI: 10.1002/ange.200504262
Cyclic Dimethylsiloxanes as Pseudo Crown
Ethers: Syntheses and Characterization of
Andreas Decken, Jack Passmore,* and Xinping Wang
In memory of Chunying Liao
Although the chemistry of silicon is notably different from
that of carbon,[1] parallels between the chemistry of the two
elements continue to emerge, for example, the recent
syntheses of a proposed SiSi triple bond,[2] persilaaromatic
rings,[3] silylium ions,[4] and silaadamantane.[5] However, few
stable adducts of silicon ethers (for example, (Me3Si)2O) have
been prepared,[6] and there have been no reports of direct
reactions of metal ions with cyclic dimethysiloxanes Dn (Dn =
(Me2SiO)n, n = 1?40)[7] or related compounds, in contrast to
the extensive and selective reaction of metal ions with the
structurally similar crown ethers.[8] Silacrown ethers containing one or two Me2SiO units have a drastically reduced ability
to bind metal cations compared to crown ethers.[9] This
observation has been attributed to the low basicity of oxygen
in siloxane compounds,[10] the reasons for which are of
continuing interest.[11] Nevertheless, two examples[12] of
[*] Dr. A. Decken, Prof. J. Passmore, X. Wang
Department of Chemistry
University of New Brunswick
Fredericton, NB E3B 6E2 (Canada)
Fax: (+ 1) 506-453-4981
[**] Acknowledgement is made to NSERC (Canada) for financial
support of this research, Mikko Rautiainen for help with calculations, and Dr. Carsten Knapp for his helpful suggestions.
Supporting information for this article is available on the WWW
under or from the author.
Angew. Chem. 2006, 118, 2839 ?2843
These results, and the calculated energies of related reactions
of alkali-metal cations with cyclic dimethysiloxanes imply the
existence of a new class of host?guest complexes for the cyclic
siloxanes that is similar to, but less extensive than, that for the
crown ethers; for example, the reaction of LiACHTUNGRE[AlPhF] and D5 in
CH2Cl2 did not give the expected product LiD5ACHTUNGRE[AlPhF].[14] In
addition, these findings imply that new classes of metal
complexes of cyclosiloxane analogues (for example, cyclophosphazenes) may be prepared by using metal salts of large
weakly coordinating anions, which minimize lattice-energy
changes and cation?anion interactions.[15]
The IR and Raman spectra of the moisture-sensitive,
thermally stable, colorless salts LiD5ACHTUNGRE[AlF], LiD6ACHTUNGRE[AlF], and
LiD6ACHTUNGRE[AlPhF] showed the characteristic peaks of the anions, as
well as peaks very similar to those of the siloxane reactants.
Electron ionization mass spectrometry (EI-MS) and chemical
analysis of the products were consistent with the given
formulations. The 29Si{1H} NMR signals of LiD6ACHTUNGRE[AlPhF] (d =
10.14 ppm) and LiD6ACHTUNGRE[AlF] (d = 9.22 ppm) in liquid SO2
were different from that of D6 (d = 22.69 ppm), implying the
presence of the [LiD6]+ ion, or an equilibrium mixture of
[LiD6]+, Li+, and D6.[16] The 29Si{1H} NMR chemical shift of
LiD5ACHTUNGRE[AlF] (d = 21.28 ppm) is similar to that of D5 (d =
21.67 ppm), indicating complete dissociation of the complex
into Li+, [AlF] , and D5 in liquid SO2. This observation is
consistent with the less negative estimated energy (DE =
210 kJ mol1, HF/6-31G*) for the reaction of LiACHTUNGRE[AlF] with
D5 [Eq. (2)] compared to that for the corresponding reaction
with D6 (DE = 242 kJ mol1; Scheme 1).[17]
LiйAlF ­sя ■ D5­lя ! LiD5 йAlF ­sя
A preliminary single-crystal X-ray diffraction (XRD)
study of LiD5ACHTUNGRE[AlF][18] clearly showed that the structure of the
[LiD5]+ ion is very similar to that calculated by ab initio and
density functional theory (DFT) methods (Figure 1, Table 1).
The solid-state structures of the [LiD6]+ ions (Figure 2) in
both LiD6ACHTUNGRE[AlF] and LiD6ACHTUNGRE[AlPhF] are similar,[19, 20] but the cation
in LiD6ACHTUNGRE[AlF] more clearly resembles the ideal gas-phase
structure, in which the Li+ ion is in the plane of the Si6O6 ring.
The distortion from the ideal structure results from Li+иииFd
interactions between the cations and the anions. The strength
of these interactions, which can be judged by calculating their
2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
out of the Si6O6 plane in LiD6ACHTUNGRE[AlPhF] (0.423(3) F) than in
LiD6ACHTUNGRE[AlF] (0.13(1) F), and to a slightly stronger coordination
of four oxygen atoms to the Li+ ion in LiD6ACHTUNGRE[AlF] (LiO
2.03(2)?2.07(1) F; s = 0.81 vu) than in LiD6ACHTUNGRE[AlPhF] (LiO
2.059(3)?2.099(4) F; s = 0.77 vu). Related compounds with
five-coordinate Li+ ions include Li([12]crown-4)Cl (LiO
2.128(2) F) and Li([12]crown-4)ACHTUNGRE[CF3SO2NACHTUNGRE(CH2)3OCH3] (Li
O 2.080(3)?2.187(3) F).[22] The cyclohexaphosphonitrile ring,
which is isoelectronic to cyclohexasiloxane, acts as a macrocyclic ligand to Cu2+ and Co2+ in the ions [{N6P6ACHTUNGRE(NMe2)12}MCl]+ (M = Cu, Co).[23] In these cations, the metal
Scheme 1. Born?Haber cycle for the reaction of LiX (X = [AlF] or I) with
atoms are coordinated by four nitrogen atoms of the cycloD6. Lattice energies DUL, energy of vaporization DEvap, binding
hexaphosphazene ring and one chlorine atom, in a coordinaenergies DEB (calculated at the HF/6-31G* level of theory), and
tion geometry that is similar to that of the lithium atoms in
energies of formation DE are given in kJ mol1.
The average SiONC bond lengths and SiONC-Si angles involving the noncoordinating
oxygen atoms (ONC) in the [LiD6]+ ions of LiD6ACHTUNGRE[AlF] and LiD6ACHTUNGRE[AlPhF] (Figure 2 c, Table 1) are
similar to those found for the oxygen atoms in D6
by electron diffraction (ED).[24] For the coordinating oxygen atoms, however, the average SiO
bond lengths are slightly longer, and the average
Si-O-Si angles are smaller. The average SiC
bond lengths for the silicon atoms adjacent to
two coordinating oxygen atoms are similar to
those for the silicon atoms adjacent to only one
coordinating oxygen atom. The average lengths
of all the SiC bonds in the [LiD6]+ ions are
slightly shorter than that in D6 (Table 1). These
differences are consistent with a strong electrostatic interaction between the lithium and
Figure 1. a) Top view and b) side view of the optimized Cs geometry of the [LiD5]+ ion;
oxygen atoms,[25] and an induced polarization
interatomic distances [E] (bold) and angles [8] (italic) calculated at the HF/6-31G* (B) and
B3LYP/6-31G* (C) levels of theory are indicated. c) Side view of the [LiD5] ion in the
of the p2(O)!s*ACHTUNGRE(SiCH3) interactions, which
preliminary crystal structure of LiD5ACHTUNGRE[AlF]. D5 = (Me2SiO)5 ; [AlF] = Al{OCACHTUNGRE(CF3)3}4. Large open Si,
leads to a slight weakening of the SiO bonds
filled crossed O, open crossed C, small open H.
and a slight strengthening of the SiC bonds
(Figure 3). The calculated natural bond orbital
(NBO) charges support this picture: upon coordination of D6
bond valence s (in valence units vu),[21] is greater in the salt of
the more basic [AlPhF] ion (s = 0.125 vu) than in LiD6ACHTUNGRE[AlF]
to the Li+ ion, the charge on the coordinating oxygen atoms
(s = 0.041 vu), leading to a greater displacement of the Li ion
becomes more negative, the charge on the SiMe2 fragments
Table 1: Experimental and calculated average distances [E] and angles [8] for the [LiD5]+ and [LiD6]+ ions, and for the free D5 and D6 molecules.
XRD ([AlF])
XRD ([AlPhF])
[a] The subscript NC denotes noncoordinating O atoms; O atoms without subscripts are coordinated to Li atoms. [b] Average length for all SiC
bonds. [c] Approximate symmetries. [d] The gas-phase structures of D5 and D6 were determined by electron diffraction (ED); the final structures are
not well defined.[24] [e] The single-crystal structure of D5 was determined by X-ray diffraction (XRD): S. Parson, D. Rankin, P. Wood, private
communication to the Cambridge Structural Database, CCDC-247844, The Cambridge Crystallographic Data Centre, 2004.
2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. 2006, 118, 2839 ?2843
Table 2: Average atomic and fragment NBO charges (q) for D6 and its
alkali-metal complexes [MD6]+ (M = Li, Na, Rb), calculated at the B3LYP/
6-31G* level of theory.
[a] The subscript NC denotes noncoordinating O atoms; O atoms
without subscripts are coordinated to M atoms. In [NaD6]+ and [KD6]+,
the M atoms are coordinated by all O atoms equally. See Supporting
Information for details. [b] Difference between the average charges
qACHTUNGRE(SiMe2) of [MD6]+ and of free D6.
coordination of the Li+ ion, the Si6O6 framework of
D6 becomes nearly planar. However, in LiD6ACHTUNGRE[AlPhF], stronger LiиииF and HиииF contacts cause
some deformation (bending) of the Si6O6 plane
(Figure 2 b).[26]
The syntheses of the LiD5ACHTUNGRE[AlF], LiD6ACHTUNGRE[AlF], and
LiD6ACHTUNGRE[AlPhF] salts are the first examples of the
preparation of host?guest complexes directly from
cyclic dimethylsiloxanes, alkali-metal ions, and
Figure 2. a) Side view of the [LiD6]+ ion in LiD6ACHTUNGRE[AlF]. b) Side view and c) top view of
weakly coordinating anions. Their structures
the [LiD6] ion in LiD6ACHTUNGRE[AlPhF]; average interatomic distances [E] (LiO, SiO, Si
imply that the cyclic dimethylsiloxanes (D5 and
ONC, O2SiC, and OACHTUNGRE(ONC)SiC; the subscript NC denotes noncoordinating O
D6) act as pseudo crown ethers and provide rare
atoms; O atoms without subscripts are coordinated to the Li atom) and angles [8]
(Si-O-Si and Si-ONC-Si) are indicated. d) Optimized C2 geometry of D6 at the HF/6examples of silicon ethers behaving as Lewis bases.
31G* level of theory. D6 = (Me2SiO)6 ; [AlF] = Al{OCACHTUNGRE(CF3)3}4 ; [AlPhF] = Al{OCThe counterpoise-corrected binding energies for
ACHTUNGRE(CF3)2Ph}4. Large open Si, filled crossed O, open crossed C, small open H.
the alkali-metal complexes [MD6]+ exhibit a
remarkable similarity to that for [18]crown-6
(Figure 4):[27] for both sets of complexes (in the gas phase),
becomes more positive, and the
charge on lithium becomes slightly
the binding energies become less negative with increasing size
less than 1, which implies a very
of the alkali-metal cation. However, the binding affinity of D6
small amount of LiO covalent
calculated at the HF/3-21G level is approximately
bonding (Table 2). Further calcula100 kJ mol1 less than that of [18]crown-6, reflecting the
tions on [MD6]+ (M = Na, K) imply
lower basicity of the siloxanes. Thus, the reaction of D6(l) with
that replacement of the Li+ ion by
LiI(s) is thermodynamically unfavorable (DE = + 66 kJ mol1;
the less polarizing Na and K ions
Scheme 1).[28] However, replacement of I by the larger ion
increases the positive charge on the
[AlF] reduces the unfavorable change in lattice energy on
metal atom, decreases the positive
charge on the SiMe2 fragments, and
Figure 3. Schematic repdecreases the negative charge on the
resentation of the polarcoordinating oxygen atoms. In conization of the OSi
trast, there is little change in the C
bond and the p2(O)!
O bond lengths and C-O-C angles in
s*ACHTUNGRE(Si-CH3) interaction
[18]crown-6 upon coordination to
upon coordination of D6
alkali-metal cations,[25] consistent
to Li+ in the [LiD6]+ ion.
with the absence of p2 !s* hyperconjugation in the crown ether.
The structure of D6 was determined in the gas phase by
ED.[24] This study suggested that the D6 ring is puckered, with
some methyl groups pointing inward (see Figure 2 d for the
geometry of D6 calculated at the HF/6-31G* level of theory).
Rotation of the inner methyl groups outward produces a
larger cavity at the center of the ring, which is occupied by Li+
in the [LiD6]+ ion (the calculated geometry of [LiD6]+ is
Figure 4. Binding energies DEB (counterpoise corrected) of D6 and
similar to that of the cation in LiD6ACHTUNGRE[AlF], Figure 2 a). Upon
[18]crown-6 with alkali-metal cations.
Angew. Chem. 2006, 118, 2839 ?2843
2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
+ 358 kJ mol1 for X = I and + 50 kJ mol1 for X = [AlF]),
and the energy of formation of LiD6ACHTUNGRE[AlF](s) from LiACHTUNGRE[AlF](s) and
D6(l) is DE = 242 kJ mol1 (Scheme 1). Thus, a new class of
salts with cyclosiloxane?metal cations and weakly coordinating anions can be anticipated.
Experimental Section
LiD5ACHTUNGRE[AlF]: CH2Cl2 (50 mL) was added to D5 (0.45 mL, 1.16 mmol)
over solid LiACHTUNGRE[AlF] (0.985 g, 1.01 mmol) in a 100-mL Schlenk flask. The
resulting colorless, clear solution was concentrated to saturation by
stirring overnight at room temperature. Large crystals were obtained
after 1 day at 20 8C. The solvent was removed under vacuum, and
the crystallized product was washed three times with n-hexane. Yield:
1.25 g (90 %, based on LiACHTUNGRE[AlF]). 29Si{1H} NMR (79.4 MHz, SO2, RT):
d = 21.28 ppm (m, D5); 13C{1H} NMR (100.6 MHz, SO2, RT): d =
0.893 ppm (s, D5); 1H NMR (400.0 MHz, SO2, RT): d = 0.125 ppm (s,
D5); 19F NMR (376.3 MHz, SO2, RT): d = 74.113 ppm (s, LiACHTUNGRE[AlF]);
Al NMR (104.2 MHz, SO2, RT): d = 35.107 ppm (s, LiACHTUNGRE[AlF]);
Li NMR (155.4 MHz, SO2, RT): d = 0.288 ppm (s, LiACHTUNGRE[AlF]). FT-IR
(KBr, solid, RT, n? assigned to [LiD5]+ marked with *, e.g. 2972 (w),*):
n? = 2972 (w),* 2907 (w),* 1626 (w), 1356 (s),* 1301 (s), 1275 (s),* 1236
(s), 1215 (vs), 1163 (m), 1026 (s; #asACHTUNGRE(SiOSi)),* 971 (vs), 855 (m),* 825
(s),* 808 (s),* 752 (m; #aACHTUNGRE(SiC2)),* 726 (s; #sACHTUNGRE(SiC2)),* 709 (m),* 666 (w;
#sACHTUNGRE(SiOSi)),* 572 (w), 568 (m), 555 (m), 534 (m), 439 (m), 401 cm1
(m). FT-Raman (RT, n? assigned to [LiD5]+ marked with *): n? = 2975
(m; #a(CH)),* 2914 (s; #s(CH)),* 1494 (w), 1402 (w), 1276 (w), 797
(w),* 745 (w),* 536 (m), 321 (w), 164 cm1 (w). EI-MS (30 eV): m/z
[M+D5CACHTUNGRE(CF3)33CF3F], 354 (100) [M+LiACHTUNGRE[AlF]Me =
D5+Me]. Elemental analysis (%) calcd: C 23.24, H 2.25; found: C
23.37, H 2.47. M.p.: 216 8C (decomp).
LiD6ACHTUNGRE[AlF]: The preparation of LiD6ACHTUNGRE[AlF] was similar to that of
LiD5ACHTUNGRE[AlF] (LiACHTUNGRE[AlF] 0.808 g, 0.830 mmol; D6 0.50 mL, 1.08 mmol;
CH2Cl2 50 mL). Yield: 1.12 g (95 %, based on LiACHTUNGRE[AlF]). 29Si{1H} NMR
(79.4 MHz, SO2, RT): d = 9.22 ppm (s, SiMe2); 13C{1H} NMR
(100.6 MHz, SO2, RT): d = 120.011 (q, JACHTUNGRE(C,F) = 291 Hz, 3 C, CF3),
79.219 (s, 1 C, OCCF3), 0.202 ppm (s, 3 C, SiMe2); 1H NMR
(400.0 MHz, SO2, RT): d = 0.296 ppm (s, SiMe2); 19F NMR
(376.3 MHz, SO2, RT): d = 75.193 ppm (s, [AlF]); 27Al NMR
(104.2 MHz, SO2, RT): d = 34.998 ppm (s, [AlF]); 7Li NMR
(155.4 MHz, SO2, RT): d = 0.190 ppm (s). IR (KBr, neat, RT, n?
assigned to [LiD6]+ marked with *): n? = 2965 (m),* 2916 (w),* 1537
(w), 1494 (w),* 1408 (m),* 1377 (w),* 1352 (s), 1300 (s), 1276 (s),*
1241 (s), 1216 (s), 1167 (s), 1132 (m), 1087 (s; #asACHTUNGRE(SiOSi)),* 1010 (s),
968 (s), 853 (s),* 822 (s),* 794 (s; #aACHTUNGRE(SiC2)),* 752 (m; #aACHTUNGRE(SiC2)),* 724
(s; #sACHTUNGRE(SiC2)),* 665 (w; #sACHTUNGRE(SiOSi)),* 619 (m; #sACHTUNGRE(SiOSi)),* 560 (m), 532
(m), 441 (m), 396 cm1 (s). Raman (RT, n? assigned to [LiD6]+ marked
with *): n? = 2975 (s; #a(CH)),* 2915 (vs; #s(CH)),* 1495 (w), 797 (w),*
745 (w),* 542 (m), 320 (w), 168 cm1 (w). EI-MS (30 eV):
m/z (%): 539 (15) [M+D6OCACHTUNGRE(CF3)3C2F8O], 522 (31)
[M+D6CACHTUNGRE(CF3)33 CF3F], 354 (100) [M+LiACHTUNGRE[AlF]Me =
D6+Me]. Elemental analysis (%) calcd: C 23.72, H 2.56; found C
23.77, H 2.60. M.p. 286 8C (decomp).
LiD6ACHTUNGRE[AlPhF]: CH2Cl2 (20 mL) was transferred onto D6 (0.45 mL,
0.97 mmol) over solid LiACHTUNGRE[AlPhF] (0.956 g, 0.95 mmol) in a 100-mL
Schlenk flask. The resulting yellowish, clear solution was stirred
overnight at room temperature. n-Hexane (40 mL) was added to the
solution, and a large amount of crystals was obtained after 1 day at
20 8C. The crystals were separated by filtration, and the filtrate was
further concentrated to one third, producing more crystals, which
were washed with n-hexane. Total yield: 1.17 g (85 %, based on
LiACHTUNGRE[AlPhF]). 29Si{1H} NMR (79.4 MHz, SO2, RT): d = 10.14 ppm (s,
SiMe2); 13C{1H} NMR (100.6 MHz, SO2, RT): d = 0.454 (s, SiMe2),
80.085 (s, OCACHTUNGRE(CF3)2Ph), 125.763 (q, JACHTUNGRE(C,F) = 291 Hz, CF3), 128.186 (s,
ortho-C6H5), 128.688(s, meta-C6H5), 129.206 (s, para-C6H5),
136.069 ppm (s, ipso-C6H5); 1H NMR (400.0 MHz, SO2, RT): d =
0.288 (s, 36 H, SiMe2), 7.898 (m, 8 H, meta-C6H5), 7.330 (m, 4 H,
para-C6H5), 7.233 ppm (m, 8 H, ortho-C6H5); 19F NMR (376.3 MHz,
SO2, RT): d = 74.119 ppm (s, [AlPhF]); 27Al NMR (104.2 MHz, SO2,
RT): d = 29.552 ppm (s, [AlPhF]); 7Li NMR (155.4 MHz, SO2, RT): d =
0.180 ppm (s). FT-IR (KBr, neat, RT, n? assigned to [LiD6]+ marked
with *): n? = 3666 (w), 3576 (w), 3062 (vw), 2963 (w),* 2899 (vw),* 1622
(m), 1502 (w), 1485 (w), 1446 (m),* 1412 (w),* 1331 (m), 1305 (s), 1266
(vs),* 1223 (s), 1193 (vs), 1198 (vs), 1133 (s), 1078 (s; #asACHTUNGRE(SiOSi)),*
1026 (s), 1001 (s; #asACHTUNGRE(SiOSi)),* 996 (vs), 966 (vs), 932 (s), 915 (m), 855
(s),* 821 (s),* 795 (s; #aACHTUNGRE(SiC2)),* 761 (m), 743 (m), 713 (vs), 688 (m),*
658 (m; #sACHTUNGRE(SiOSi)),* 619 (w), 559 (w), 538 (w), 495 (w), 435 (m),
396 cm1 (m). FT-Raman (RT, n? assigned to [LiD6]+ marked with *):
n? = 3084 (s), 2967 (s; #a(CH)),* 2909 (vs; #s(CH)),* 1604 (w), 1495
(w), 1171 (w), 1038 (m), 1005 (m),* 786 (w), 735 (w), 619 (w),*
542 cm1 (m). EI-Ms (30 eV): m/z (%): 918 (92) [M+D6CF3F],
901 (100) [M+D6CF32F], 429 (40) [M+LiACHTUNGRE[AlPhF]Me =
D6+Me]. Elemental analysis (%) calcd: C 39.72, H 3.89; found: C
39.70, H 3.84. M.p.: 132 8C (decomp).
The following are given in the Supporting Information: general
experimental techniques; a description of the reaction designed to
produce Se6Ph2ACHTUNGRE[AlF]2, from which crystals of LiD6ACHTUNGRE[AlF] were isolated;
a comparison of the FT-IR, FT-Raman, and NMR spectra of
LiD5ACHTUNGRE[AlF], LiD6ACHTUNGRE[AlF], and LiD6ACHTUNGRE[AlPhF] with those of the reactants;
different views of the crystal structures of LiD5ACHTUNGRE[AlF], LiD6ACHTUNGRE[AlF], and
LiD6ACHTUNGRE[AlPhF]; and details of the calculations.
Received: November 30, 2005
Published online: March 20, 2006
Keywords: crown compounds и host?guest systems и lithium и
siloxanes и weakly coordinating anions
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2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. 2006, 118, 2839 ?2843
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and references therein.
CH2)]}2] were obtained accidentally upon crystallization of
KACHTUNGRE[InHACHTUNGRE(CH2tBu)3] from heptane or during the metallation of
HCACHTUNGRE(SiMe3)2ACHTUNGRE[SiMe2ACHTUNGRE(CH=CH2)] with methylpotassium, respectively, both in the presence of silicone grease: a) M. R. Churchill,
C. H. Lake, S. H. Chao, J. O. T. Beachley, J. Chem. Soc. Chem.
Commun. 1993, 1577; b) C. Eaborn, P. B. Hitchcock, K. Izod,
J. D. Smith, Angew. Chem. 1995, 107, 2936; Angew. Chem. Int.
Ed. Engl. 1995, 34, 2679.
Silicone grease consists principally of polydimethylsiloxane
ACHTUNGRE(>80 %), dimethylcyclosiloxane (< 1 %, ring size unknown),
and hydroxy-terminated dimethylsiloxane (ca. 5?10 %).[12a] For
silicone grease as a serendipitous reagent, see: I. Haidue,
Organometallics 2004, 23, 3.
Single-crystal XRD and FT-IR spectroscopic analysis of the
product showed it to be a new polymorph of the starting material
LiACHTUNGRE[AlPhF]. See Supporting Information for details.
a) S. H. Strauss, Chem. Rev. 1993, 93, 927; b) C. Reed, Acc.
Chem. Res. 1998, 31, 133; c) I. Krossing, I. Raabe, Angew. Chem.
2004, 116, 2116; Angew. Chem. Int. Ed. 2004, 43, 2066; d) T. S.
Cameron, A. Decken, I. Dionne, M. Fang, I. Krossing, J.
Passmore, Chem. Eur. J. 2002, 8, 3386; e) T. S. Cameron, J.
Passmore, X. Wang, Angew. Chem. 2004, 116, 2029; Angew.
Chem. Int. Ed. 2004, 43, 1995.
The associative?dissociative process of metal cation/crown ether
complexes in solution has been well determined: M. K. Amini,
M. Shamsipur, J. Phys. Chem. 1991, 95, 9601, and references
For details of reaction-energy calculations, see Supporting
Information. Gaussian 03, Revision C.02, J. A. Pople, et al.
Gaussian, Inc., Wallingford CT, PA, 2004.
LiD5ACHTUNGRE[AlF] crystallizes in the monoclinic space group P21/c, with
a = 10.9596(9), b = 28.564(2), c = 17.028(1) F, b = 97.324(2)o,
V = 5302(2) F3, and Z = 4. The structure was not completely
determined, because of disorder in the anion.
Structure determination of LiD6ACHTUNGRE[AlF]: Bruker AXS P4/SMART
1000 diffractometer, graphite-monochromatized MoKa radiation
(l = 0.71073 F), T = 173(1) K, P1?, Z = 4, a = 11.0053(19), b =
22.828(4), c = 24.398(5) F, a = 101.660(4), b = 102.974(3), g =
103.558(3)8, V = 5592.7(18) F3, 1calcd = 1.664 mg m3, 2 qmax =
50.08, 26 311 reflections collected, 17 449 independent reflections, 1485 parameters, R1ACHTUNGRE(I>2 s) = 0.1049, R1ACHTUNGRE(all data) =
0.1422. There are two symmetry-independent [LiD6]+ ions in
LiD6ACHTUNGRE[AlF], one of which is shown in Figure 2 a. The main
difference between the two cations is the differing strength of
their LiиииF contacts (3.02(2) and 3.19(2) F for the [LiD6]+ ion
not shown in Figure 2 a). The structure of LiD6ACHTUNGRE[AlF] was not well
determined, owing to severe rotational disorder in the anion,
which prevents precise comparison with that of LiD6ACHTUNGRE[AlPhF].
Structure determination of LiD6ACHTUNGRE[AlPhF]: Bruker AXS P4/
SMART 1000 diffractometer, graphite-monochromatized MoKa
radiation (l = 0.71073 F), T = 173(1) K, P1?, Z = 2, a =
11.9673(9), b = 15.9362(12), c = 17.7554(12) F, a = 88.198(2),
b = 87.127(2),
g = 72.045(1)o,
V = 3216.8(4) F3,
1calcd =
1.498 mg m3, 2 qmax = 55.08, 22 472 reflections collected, 14 017
independent reflections, 823 parameters, R1ACHTUNGRE(I>2 s) = 0.0416,
Angew. Chem. 2006, 118, 2839 ?2843
R1ACHTUNGRE(all data) = 0.0667. CCDC-291338 (LiD6ACHTUNGRE[AlF]) and CCDC291339 (LiD6ACHTUNGRE[AlPhF])contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
The bond valences s (in valence units vu) are defined as s =
expACHTUNGRE[(RoR)/B], where R is the observed distance, Ro is the
covalent bond length of the bond (bond order = 1; for LiF, Ro =
1.36 F; for LiO, Ro = 1.466 F), and B is an empirical parameter
set to 0.37. a) I. D. Brown in Structure and Bonding in Crystals,
Vol. 2 (Eds.: M. OSKeefe, A. Navrotsky), Academic Press,
London, 1981; b) I. D. Brown, The Chemical Bond in Inorganic
Chemistry (The Bond Valence Model), Oxford University Press,
Oxford, 2002.
a) F. Gingl, W. Hiller, J. Strahle, H. Borgholte, K. Dehnicke, Z.
Anorg. Allg. Chem. 1991, 606, 91; b) R. E. A. Dillon, C. L. Stern,
D. F. Shriver, Chem. Mater. 2000, 12, 1122.
a) W. C. Marsh, N. L. Paddock, C. J. Stewart, J. Trotter, J. Chem.
Soc. D 1970, 1190; b) W. C. Marsh, J. Trotter, J. Chem. Soc. A
1971, 1482; c) W. Harrison, J. Trotter, J. Chem. Soc. Dalton. 1973,
H. Oberhammer, W. Zeil, J. Mol. Struct. 1973, 18, 309.
NBO and natural energy decomposition analysis of alkali-metal
complexes of [18]crown-6 indicated that electrostatic interactions and polarization are the dominant bonding forces between
the host and guest; the contribution of charge transfer is much
less important: E. D. Glending, D. Feller, M. A. Thompson, J.
Am. Chem. Soc. 1994, 116, 10 657.
The angle between the O1-O2-O6 and O3-O4-O5 planes in
LiD6ACHTUNGRE[AlPhF] is 144.4(1)8. To investigate the influence of the LiиииF
and HиииF contacts in LiD6ACHTUNGRE[AlPhF] on the geometry of [LiD6]+ ion,
we calculated the optimized geometry for the hypothetical
complex LiD6F. The initial geometry of LiD6F contained a
planar [LiD6]+ ion, with a F ion bonded to the lithium atom.
Optimization led to a bent geometry, confirming that the
geometry of the [LiD6]+ ion in LiD6ACHTUNGRE[AlPhF] is remarkably
affected by strong LiиииF and HиииF contacts. See Supporting
Information for details.
The binding affinity for [18]crown-6 with the alkali-metal cations
Li+, Na+, K+, and Rb+ was taken from ref. [25].
For the vaporization energy DEvap, see: D. F. Wilcock, J. Am.
Chem. Soc. 1946, 68, 691. The lattice energies UL for LiX and
LiD6X (X = [AlF], I) were estimated using Jenkins and PassmoreSs
UL = 2 IACHTUNGRE[(a/V1/3) + b]
[kJ mol ], where a = 117.3 kJ mol nm, b = 51.9 kJ mol1,
V [nm3] is the volume of the corresponding salt, and I is the
sum of the ionic strength: H. D. B. Jenkins, H. K. Roobottom, J.
Passmore, L. Glasser, Inorg. Chem. 1999, 38, 3609.
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crown, cyclic, ethers, synthese, 2ph, pseudo, characterization, dimethylsiloxane, me2sio, cf3
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